An innovative rotary tool technology for rapid heat cycle molding

In recent years rapid heat cycle molding (RHCM) has been increasingly used to improve the surface quality of molded plastic products. For a given product the average cycle time of a RHCM process is nearly as long as the one measured in conventional injection molding. In this work an innovative rotary tool technology was developed in order to drastically reduce the cycle time. The equipment consists of a molding cavity heated up to a high temperature, a rotary plate with two cores conditioned at the standard processing temperature and a dummy cavity at cold temperature. Initially the polymer is injected between the hot cavity and the core in the first station. Then the mold is opened and the part is trasfered to the second station. The mold is closed and the part is packed and cooled by the cold cavity. In the meantime a new polymer melt is injected in the first cavity. To test the proposed technology, a rotary mold for a large TV frame was realized. The experimental results show that the proposed RHCM technique allows to achieve high-temperature injection molding, improve cooling efficiency and drastically reduce molding cycle time without affecting part quality. Experimental tests with different cavity and core temperatures were carried out to optimize the warpage of the TV panel. Numerical simulations were used to analyze the cooling phase and to predict the warpage of the part.